Production Of Lead Zirconate Titanate Research Articles

Role of Impurities in the Sintering Behavior and Properties of Lead Zirconate Titanate Ceramics

Small amounts of impurities are always present in the raw materials for the mass production of lead zirconate titanate (PZT) ceramics. In this work, the effects of these impurities on sintering kinetics were investigated. The sintering behavior of PZT ceramics was monitored in situ by a thermo‐optical measuring device. Two sources of raw materials were used, industrially used and highly pure (99.99%) powders. The highly pure powders were doped with different impurities, characteristic of industrially used materials. Sintering was enhanced by Si and—to a smaller extent—by Na, Ca, and Ba. Hf can have a large impact, if the stoichiometry is not adjusted properly according to its concentration. In addition, the crystal phase of the titania component affected its reactivity and lead loss during calcination, which indirectly changed the sintering behavior. The effects of the impurities on the dielectric and piezoelectric properties were also discussed.

Effects of rheology on the interface of Pb(Zr, Ti)O 3 monofilament composites obtained by co-extrusion

The production of lead zirconate titanate (PZT) fibres, 1-3, 3-1 and 2-2 composites for actuator and sensor applications through the thermoplastic co-extrusion process can be achieved by using a macro-scale preform shaped by two different extrudable mixtures. The main challenge of this method is the optimization of materials that can be co-extruded and at the same time maintain the preform geometry in the final product, without axial and cross-sectional deformation. In this work, rheological characterizations of PZT/polyethylene and carbon black/polyethylene feedstocks were carried out to produce monofilament composites by the co-extrusion process. To explore the interface instabilities resulting from the viscosity mismatch between the processed materials, the co-extrusion tests were performed varying the velocity of the piston during extrusion. Successful co-extrusion, with well preserved fibre morphologies and defined interface between the co-extruded materials, was achieved for viscosity ratios between the feedstocks ranging from 0.98 to 1.16. Outside of this range, interface distortions were observed.

Low temperature hydrothermal routes to various PZT stoichiometries

The production of lead zirconate titanate (PZT) with a variation in Zr and Ti ratios using a hydrothermal method has been attempted. We show that when reactions are conducted at 160 °C, for 4 h, the phase of PZT produced is independent of the initial Zr/Ti precursor ratio. In all cases we produce PZT with a crystal structure close to the morphotropic phase boundary, i.e. Zr/Ti ≈ 52:48. The excess precursors either fail to react, or form amorphous and crystalline impurity phases that are detectable via powder XRD after the hydrothermal treatment. Using an excess of Pb precursor is shown to aid the crystallisation of the resultant PZT powder, as verified by SEM and FIB analysis.

PZT thin film deposition on Si wafers and optical fibers prepared by reactive DC pulsed magnetron sputtering from a single metallic target

A metallic target was utilized to produce lead zirconate titanate (PZT) thin films by reactive DC pulsed magnetron sputtering on either Ti/Pt(111)/Ti-coated Si wafers at 490 °C or optical glass fibers at 500 °C. Multicrystalline PZT thin films were obtained by applying both conventional annealing (CA) at 650–720 °C in air and rapid thermal annealing (RTA) at 550–700 °C in vacuum. The morphological, structural, and chemical properties of post-annealed PZT have been examined as a function of the annealing temperature and time. Homogeneous, dense and crack-free specimens were produced by CA at 690 °C for 2 h. Low micro-crack formation was observed when PZT-coated wafers were annealed at 550–700 °C by applying RTA. X-ray photoelectron spectroscopy reveals an excess of Pb in the top layer of the surface. The chemical environments of the elements did not change significantly during annealing. First deposition experiments with optical fibers were conducted. Although CA at 650 °C resulted in the successful formation of PZT, scanning electron micrographs showed blister and crack formation.

Particle Formation During Spray Pyrolysis of Lead Zirconate Titanate

A twin‐fluid atomization spray pyrolysis technique has been used to produce lead zirconate titanate (PZT) powders from a sol–gel precursor solution. Samples were removed from ports sited along the reactor in order to examine particle development at progressive stages of pyrolysis. The total time in the reactor was 2.6 s. The size and shape of the particles showed no change between the first port (190°C) and the hottest part of the reactor (820°C), indicating that the physical structure of the particles was established during the initial drying stages. The powders were mainly composed of spherical particles, but irregular forms were also present, which were thought to result from the inward collapse of hollow gelatinous particles. Crystallization of PZT commenced at around 700°C, initially to a pyrochlore or fluorite intermediate phase, with the desired perovskite phase developing between 790°C and 815°C. However, a minor amount of the pyrochlore/fluorite phase persisted in the final powder. The final powders also contained basic lead carbonate, 2PbCO3·Pb(OH)2, which existed in the form of elongated crystallites on the surface of the PZT particles.

Formation of Lead Zirconate Titanate Powders by Spray Pyrolysis

Twin‐fluid atomization spray pyrolysis (SP) has been investigated for the production of lead zirconate titanate (PZT) powders, using aqueous solutions of lead acetate and zirconium and titanium alkoxide precursor reagents. The particle size distribution of the PZT powder showed a d50 value of 0.3 μm, but with a small fraction of relatively large particles, several micrometers in size. Most particles were spherical but many of the largest particles, in the size range ca. 1–5 μm, were irregular. It was demonstrated that the morphology of the final PZT powder was controlled by decomposition processes occurring during the initial drying stages, at ≤200°C. A pyrochlore or fluorite‐type intermediate crystalline phase was present in the final powders, but when the maximum reactor temperature was raised, and/or when the levels of excess lead in the starting solutions were increased, the proportion of the desired perovskite phase increased. However, at the highest process temperatures studied, ∼900°C, small crystallites of another phase formed on the surface of the PZT particles; these were probably lead oxide carbonate particles. Overall, a starting solution composition containing around 5 mol% excess Pb, and a maximum reactor temperature of 800°C, were selected as offering the most suitable conditions for producing PZT (52/48) powder, with minimal secondary phases(s). Preliminary densification studies showed that the powders could be sintered at 1150°–1200°C to give pellets of 95%–96% theoretical density.

Production of piezoceramic powders by the thermal two-stage process

The present paper describes the production of lead zirconate titanate (PZT) with different additives and of lead metaniobate (PN) by means of the Thermal Two-Stage Process. This process, especially developed for the synthesis of multicomponent ceramic powders is characterized by the following: the starting constituents are liquid metalorganic precursors, such as alcoholates or acetates, which are converted to a homogeneous, multicomponent ceramic powder by spray drying the liquid precursors, resulting in an organic granulate, which is then followed by the thermal conversion of this organic powder into the final ceramic material. The resulting ceramic powder shows favourable properties with respect to homogeneity and further processing, e.g. pressing and sintering of compacts. The efficiency of the process will be demonstrated by the characterization of the piezoelectric properties of the sintered compacts.

Effects of metal salts on the thermal decomposition of edta-gel precursors for ferroelectric ceramic powders

Raw chemicals such as metal nitrates and chlorides were found to affect the thermal decomposition behaviour of EDTA-gel precursors used for the production of ceramic powders. Fine, homogeneous ceramic powders were produced from nitrate solutions while chlorides gave segregated phases. In studies on the production of lead zirconate titanate (PZT) using chlorides, the segregation and loss of lead was observed and shown to be caused by the formation and evaporation of PbCl2. Thermal analysis (DTA/TG) quantitatively proved the suggested reaction mechanism for this phase segregation. Crystallization of the desired perovskite phase of lead zirconate titanate (PZT) and barium titanate (BT) initiated at temperatures as low as 250°C in the nitrate-EDTA precursors. Water of crystallization and formation of BaCO3 in the barium titanate precursor were suggested to account for differences in the observed decompositional behaviours of the BT and PZT precursors.